Workflow Caching in GitHub Actions

Introduction

In this lesson, we will explore the concept of workflow caching in GitHub Actions, which helps speed up your workflows by storing and reusing dependencies or build outputs.

What is Caching?

Caching is a mechanism for storing data temporarily so that future requests for that data can be served faster. In the context of GitHub Actions, caching allows you to save the results of previous runs, reducing the time it takes to run workflows.

How Caching Works

GitHub Actions caching utilizes a key-value store to save and retrieve cached items. The cache is identified by a unique key, which you can define based on the dependencies or outputs you want to cache.

Cache Key

The cache key is a unique identifier for the cache. You can create a cache key using a combination of static strings and dynamic values, such as a hash of your dependencies file.

Cache Restore

When a workflow job runs, it first attempts to restore the cache using the provided key. If a matching cache is found, it will be used; otherwise, the job will proceed without the cache.

Cache Save

At the end of the job, you can save the cache using the cache save step. This will store the specified files or directories under the defined cache key.

Setting Up Caching

To set up caching in your GitHub Actions workflow, follow these steps:

Example Workflow

Here's an example of a GitHub Actions workflow that sets up caching for Node.js dependencies:

name: CI

on:
  push:
    branches:
      - main

jobs:
  build:
    runs-on: ubuntu-latest

    steps:
      - name: Checkout code
        uses: actions/checkout@v2

      - name: Cache Node.js modules
        uses: actions/cache@v2
        with:
          path: ~/.npm
          key: ${{ runner.os }}-node-${{ hashFiles('**/package-lock.json') }}
          restore-keys: |
            ${{ runner.os }}-node-

      - name: Install dependencies
        run: npm install

      - name: Run tests
        run: npm test

      - name: Save Node.js modules cache
        uses: actions/cache@v2
        with:
          path: ~/.npm
          key: ${{ runner.os }}-node-${{ hashFiles('**/package-lock.json') }}
        

Best Practices

To maximize the benefits of caching, consider the following best practices:

FAQ